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[Biochemistry](https://durgical.com/en/biochemistry/) · Molecule

# α-Amanitin

α-Amanitin is the toxin of mushrooms such as Amanita phalloides; it blocks RNA polymerase II and destroys liver cells.

Updated 2026-11-01

## Key facts

- It strongly inhibits RNA polymerase II, Pol III less and Pol I not at all.
- Without mRNA synthesis, highly active cells (hepatocytes, renal tubule) die.
- Enterohepatic circulation: the liver takes it up (OATP1B3 transporter), excretes it in bile and reabsorbs it, repeating the damage.
- Typical course: gut symptoms at 6–24 h, apparent recovery, then liver failure at 2–4 days.

**Also called**
Amatoxin

**Formula**
C39H54N10O14S

## Structure

- A bicyclic octapeptide with a tryptathionine bridge (tryptophan–cysteine) that makes it very stable to heat and digestion.
- It contains unusual hydroxylated amino acids; it survives cooking, freezing and drying.
- It binds the large Pol II subunit (RPB1) near the 'bridge helix' and stalls translocation.

## Clinical notes

- Responsible for most deaths from eating wild mushrooms worldwide.
- Management includes intensive support, measures to break enterohepatic circulation, silibinin or penicillin in some protocols, and liver transplantation in severe failure.
- It is being studied linked to antibodies (conjugates) as a weapon against tumour cells.

## Related conditions

- [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/)
- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)

## Related

- [RNA polymerases I, II and III](https://durgical.com/en/biochemistry/enzymes/rna-polymerases-i-ii-and-iii/)
- [Transcription](https://durgical.com/en/biochemistry/topics/transcription/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which enzyme does α-amanitin inhibit?

RNA polymerase II (and to a lesser degree Pol III), which halts mRNA synthesis.

## Why does Amanita poisoning mainly damage the liver?

Hepatocytes take up the toxin via OATP1B3 and recycle it through the enterohepatic circulation.

## What timeline is typical of amatoxin poisoning?

Gastroenteritis hours later, a false recovery, then liver failure at 2–4 days.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Alpha-Amanitin (CID 9543442)](https://pubchem.ncbi.nlm.nih.gov/compound/9543442) (PubChem, NCBI, 2026) · Public domain; [POLR2A: DNA-directed RNA polymerase II subunit RPB1 (human)](https://www.uniprot.org/uniprotkb/P24928/entry) (UniProt, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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